Understanding AMD GPU Output P-States on Linux

Understanding AMD GPU Output P-States in Linux

AMD GPUs have a feature called P-States, which stands for Performance States. These states control the clock speed and voltage of the GPU to manage power consumption and performance. Understanding how P-States work in Linux can be helpful for tasks such as GPU overclocking.

What are P-States?

P-States are a way to control the performance and power consumption of a GPU. They are used to set the clock speed and voltage of the GPU. A higher clock speed and voltage will result in higher performance but also higher power consumption. Conversely, a lower clock speed and voltage will result in lower performance but also lower power consumption.

How do P-States work in Linux?

In Linux, P-States are controlled by the AMDGPU driver. The driver exposes a set of power management interfaces that allow the user to control the P-States of the GPU. These interfaces can be accessed through the sysfs file system, which is a virtual file system that provides an interface to kernel data structures.

The AMDGPU driver supports two types of P-States: fixed and dynamic. Fixed P-States are predefined clock speeds and voltages that are set at boot time and cannot be changed at runtime. Dynamic P-States, on the other hand, can be changed at runtime and are used to adjust the clock speed and voltage of the GPU based on the current workload.

How to control P-States in Linux?

To control P-States in Linux, you can use the amdgpu_pm utility. This utility provides a command-line interface to the power management interfaces exposed by the AMDGPU driver. You can use it to set the clock speed and voltage of the GPU, as well as to enable or disable dynamic P-States.

Here is an example of how to use the amdgpu_pm utility to set the clock speed of the GPU to 700 MHz:

In this example, the --set-pp-frequency option is used to set the clock speed of the GPU. The first argument (0) specifies the P-State index, and the second argument (700) specifies the clock speed in MHz. Note that the index 0 corresponds to the minimum P-State, and the index N-1 corresponds to the maximum P-State, where N is the total number of P-States.

GPU Overclocking in Linux

GPU overclocking is the process of increasing the clock speed of the GPU beyond its stock settings. This can result in higher performance, but it also increases the power consumption and the risk of overheating. Overclocking should be done with caution and under controlled conditions.

In Linux, GPU overclocking can be done by increasing the clock speed of the maximum P-State. This can be done using the amdgpu_pm utility, as shown in the following example:

In this example, the clock speed of the maximum P-State is set to 900 MHz. Note that this value is just an example, and the actual maximum clock speed of your GPU may be different.

• P-States are a way to control the performance and power consumption of an AMD GPU
• P-States are controlled by the AMDGPU driver in Linux
• P-States can be controlled using the amdgpu_pm utility
• GPU overclocking can be done by increasing the clock speed of the maximum P-State

References

• AMDGPU - ArchWiki